Retaining walls can be constructed in a variety of ways. Cantilever walls are generally constructed as a massive, unitary "L" shaped wall, with the retained earth behind the "L" supported by the wall, and the foot of the "L" bearing the pressure exerted against the face of the wall by the earth stacked behind the "L". Because of their massive, unitary nature, these walls are generally constructed on-site using reinforced concrete, are costly, and allow the build-up of pressure behind the wall as the earth settles.
Some of the cost and mass of a cantilever wall can be reduced by eliminating the foot of the "L" and anchoring the wall to the rear of the formation as shown in U.S. Pat. Nos. 4,407,611 and 4,154,554. However, these "tie-back" retaining walls may be undesirable because, like the cantilever retaining walls, much of the weight of the soil behind the wall is borne by the face of the wall. If the anchor to the deadman is cut or breaks, the wall could be pushed over causing the earth behind it to collapse.
In contrast, reinforced soil embankment walls use means to reinforce the earth in layers. This makes the mass of earth a cohesive structure since the frontal zone of the retained formation is reinforced by its own weight against mechanical soil reinforcements, such as wire mats, spaced horizontally throughout the formation, and anchored to the more stable rear portion of the formation. Because the earthen formation is reinforced against itself, a massive retaining wall is unnecessary, and a relatively light weight, primarily decorative wall can be used to cover the face of the formation to prevent erosion. Such a facing wall is typically connected to the mechanical soil reinforcements, and may be constructed using prefabricated, interlocking facing wall panels.
Prior art mechanical soil reinforcements have included wire mats and flat metal strips which are attached to the wall and extend back horizontally into the earthen formation as shown in U.S. Pat. Nos. 4,117,686 and 4,116,010. However, such reinforcements typically are constructed from metal, have a large surface area exposed to the soil and are subject to destructive corrosion. Further, such reinforcements, because of their large exposed surface area, are forced downward during soil compaction and later by the weight of the settling earth, creating tension in the connections to the rigid facing wall or facing panels to which the soil reinforcements have been attached.
Generally, such a wall will be constructed by placing the first row of wall panels, filling in a layer of compacted earth behind the panels, placing soil reinforcements on top of the layer of compacted earth and attaching them to the wall. Then the next course of the wall is built by placing another row of wall panels atop the first row of wall panels, and adding another layer of compacted earth on top of the reinforcements. The process is then repeated until the wall is finished.
During and following construction, the wall is subjected to internal stresses due to compression from settling of the layers. The amount of compression from settling depends upon the amount of compaction during construction, the height of the finished wall, and the amount of overburden pressure. Because the rigid concrete facing panels do not settle as the earth layers settle, the connections between the soil reinforcements and the facing panels are stressed as the reinforcements are forced downward by the settling soil. This stress has caused wall failures when the earth layers are poorly compacted during construction and when the wall is subjected to external stresses, for example, earthquakes.
To prevent such destructive loading, the lateral forces on the wall from the front of the formation have been relieved by relaxing somewhat the attachment of the reinforcements to the wall, for example, as shown in U.S. Pat. No. 4,343,572.
Thus, the need exists for a means for reinforcing a soil reinforced embankment wall using reinforcements which frictionally reinforce the layers of earth effectively but which are designed to reduce stress on the connections between the facing panels and the reinforcements.